Some ways are intellectual property rights. It is having a full proof right on property. Like coca Cola is in market from 1891 but no one knows the secret formula for its syrup. Nobody can make a cold drink like coca Cola that is a entry barrier. Others ways are patent and licensing method. This is used mostly in pharmaceutical company the medicine Invented and licensed by them will only be sold by the inventing company and no other company can sell it.
Next way is the economies of scale which means buying products or raw materials in so bulk that cost per unit decreases and then presenting the finished product on competitively low priced. Your competitors will not be able to sell on your price and customers will choose you because they are getting same product at low price